In Patent Document 1 is disclosed a driving device for reciprocating a drive shaft in axial directions by expansion and contraction of an electromechanical transducer element and sliding, on the drive shaft, a movable member that frictionally engages with the drive shaft, wherein the device performs self-maintenance by moving the movable member across a total length of the drive shaft for purpose of cleaning the drive shaft as well as positioning the movable member.
In such a driving device, not only may a driving force be decreased by soil on the drive shaft but continuation of nonuse may temporarily increase a frictional force of the movable member against the drive shaft, thus making it difficult or impossible to move the movable member. That is, there may be caused a phenomenon in which the movable member sticks to the drive shaft.                Patent Document 1: JP 2004-15864 A        Patent Document 2: JP 2004-104919 A        